The present invention generally relates to manufacturing of electric and electronic apparatuses and more particularly to a solder alloy of various forms used for soldering electric and electronic components, as well as to a soldering process and further to a rig used for such a soldering process. In particular, the present invention relates to a lead-free solder alloy that contains no substantial amount of lead (Pb).
Solder alloys are characterized by low melting temperatures and provide excellent electric as well as mechanical properties. Thus, solder alloys of various forms, including solder powders and solder pastes, are used for mounting electronic components on a printed circuit board.
Meanwhile, conventional solder alloys contain Pb. As Pb is toxic against biological bodies, it has been necessary to take precautionary measure when conducting such a soldering process, while such a precautionary measure increases the cost of the products produced as a result of the soldering. Thus, there is a demand for a lead-free solder alloy that is suitable for use in various soldering processes including automated soldering process.
In the automated soldering process of electronic components, several types of solder alloys are used conventionally. A representative example is a solder alloy known as Sn63xe2x80x94Pb37, wherein the solder alloy contains 63 wt % of Sn and 37 wt % of Pb. This material causes an eutectic melting at a melting temperature of 183xc2x0 C. Another typical example is a solder alloy known as Sn62xe2x80x94Pb36xe2x80x94Ag2, wherein the solder alloy contains 62 wt % of Sn, 36 wt % of Pb and 2 wt % of Ag. The solder alloy forms an eutectic system characterized by a melting temperature of 179xc2x0 C. As these solder alloys have low melting temperatures and provide excellent mechanical properties in terms of tensile strength and elongation as well as excellent electrical properties such as low resistance, they are used extensively for various automated soldering processes.
Meanwhile, there is a tendency of increasing public regulations against the use of Pb in view of human health and in view of environmental protection. Under such circumstances, various efforts have been made for developing a substitute solder alloy that is free from Pb.
As the material for use in assembling electric and electronic apparatuses, such a substitute solder alloy is required to have a low melting temperature such that the soldered electric or electronic component experiences little degradation of performance caused by the heat at the time of soldering. Further, such a substitute solder alloy should have an excellent mechanical strength comparable to that of a conventional solder alloy that contains Pb.
Accordingly, it is a general object of the present invention to provide a novel and useful solder alloy of various forms as well as a soldering process wherein the foregoing problems are eliminated.
Another and more specific object of the present invention is to provide a solder alloy free from Pb and still having a sufficiently low melting temperature, high conductivity and high mechanical strength.
Another object of the present invention is to provide a lead-free solder alloy composition comprising Sn, Bi and In, said solder alloy containing Sn, Bi and In with respective concentrations set such that said lead-free solder alloy composition has a melting temperature lower than a predetermined heat-resisitant temperature of a work to be soldered.
Another object of the present invention is to provide a method for soldering a work, comprising the steps of:
reflowing a lead-free solder alloy containing therein Sn, Bi and In with respective contents set such that said solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of said work, said step of reflowing including a step of heating said solder alloy to a temperature higher than said melting temperature; and
cooling said work at a part where a soldering has been made to solidify said lead-free solder alloy.
Another object of the present invention is to provide a lead-free solder alloy composition containing: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a balancing component of said lead-free solder alloy.
Another object of the present invention is to provide a soldering process of a work, comprising the steps of:
reflowing a lead-free solder alloy containing therein: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said solder alloy; and
cooling said work at a part where a soldering is made to solidify said lead-free solder alloy.
Another object of the present invention is to provide a lead-free solder alloy composition containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide a method of soldering a work, comprising the step of:
reflowing a lead-free solder alloy containing therein Sn, Ag and Bi with respective contents set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resisitant temperature of said work, said step of reflowing including a step of heating said lead-free solder alloy to a temperature higher than said melting temperature; and
cooling said work at a part where a soldering is made to solidify said lead-free solder alloy.
Another object of the present invention is to provide a lead-free solder powder comprising:
a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm;
each of said lead-free solder particles containing Sn, Bi and In, with respective concentrations set such that said lead-free solder particle has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide a lead-free solder powder comprising:
a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm;
each of said lead-free solder particles containing Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said lead-free solder particle.
Another object of the present invention is to provide a lead-free solder powder comprising:
a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm;
each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered.
Another object of the present invention is to provide lead-free solder paste, comprising:
a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm; each of said lead-free solder particles containing Sn, Bi and In, with respective concentrations set such that said lead-free solder particle has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered, said solder powder being contained with a proportion of 80.0-95.0 wt %; and
a mixture of an amine halide, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.
Another object of the present invention is to provide a lead-free solder paste, comprising:
a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm; each of said lead-free solder particles containing Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said solder alloy; said lead-free solder powder being contained with a proportion of 80.0-95.0 wt %; and
a mixture of an amine halide, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.
Another object of the present invention is to provide a lead-free solder paste, comprising:
a lead free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm; each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder particle has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered; and
a mixture of an amine halide, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.
Another object of the present invention is to provide a lead-free solder paste, comprising:
a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm; each of said lead-free solder particles containing Sn, Bi and In, with respective concentrations set such that said lead-free solder powder has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered, said lead-free solder powder being contained with a proportion of 80.0-95.0 wt %; and
a mixture of an organic acid, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.
Another object of the present invention is to provide a lead-free solder paste, comprising:
a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm; each of said lead-free solder particles containing Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said solder alloy; said lead-free solder powder being contained with a proportion of 80.0-95.0 wt %; and
a mixture of an organic acid, a polyhydric alcohol and a polymer, with a proportion of 20.0-5.0 wt %.
Another object of the present invention is to provide a lead-free solder paste, comprising:
a lead-free solder powder comprising a plurality of lead-free solder particles each having a generally spherical shape with a diameter of 20-60 xcexcm; each of said lead-free solder particles containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a work to be soldered; and
a mixture of an organic acid, a polyhydric alcohol and a-polymer, with a proportion of 20.0-5.0 wt %.
Another object of the present invention is to provide a printed circuit board, comprising:
a substrate;
a conductor pattern provided on said substrate; and
a lead-free solder alloy covering said conductor pattern, said lead-free solder alloy containing Sn, Bi and In, with respective concentrations set such that lead-free said solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a component to be soldered upon said substrate.
Another object of the present invention is to provide printed circuit board, comprising:
a substrate;
a conductor pattern provided on said substrate; and
a lead-free solder alloy covering said conductor pattern, said lead-free solder alloy containing: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said lead-free solder alloy.
Another object of the present invention is to provide a printed circuit board, comprising:
a substrate;
a conductor pattern provided on said substrate; and
a lead-free solder alloy covering said conductor pattern, said lead-free solder alloy containing: Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of a component to be soldered upon said substrate.
Another object of the present invention is to provide an electronic component, comprising:
an electronic component body;
an electrode projecting from said electronic component body; and
a lead-free solder alloy covering said electrode, said lead-free solder alloy containing Sn, Bi and In, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of said electronic component.
Another object of the present invention is to provide an electronic component, comprising:
an electronic component body;
an electrode projecting from said electronic component body; and
a lead-free solder alloy covering said electrode, said lead-free solder alloy containing: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said lead-free solder alloy.
Another object of the present invention is to provide an electronic component, comprising:
an electronic component body;
an electrode projecting from said electronic component body; and
a lead-free solder alloy covering said conductor pattern, said lead-free solder alloy containing: Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined-heat-resistant temperature of a component to be soldered upon said substrate.
Another object of the present invention is to provide an electronic apparatus, comprising:
a substrate;
a conductor pattern provided on said substrate;
an electronic component mounted upon said substrate in electrical connection with said conductor pattern, said electronic component having an electrode projecting therefrom; and
a lead-free solder alloy connecting said electrode to said conductor pattern, said lead-free solder alloy containing Sn, Bi and In, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of said electronic component.
Another object of the present invention is to provide an electronic apparatus, comprising:
a substrate;
a conductor pattern provided on said substrate;
an electronic component mounted upon said substrate in electrical connection with said conductor pattern, said electronic component having an electrode projecting therefrom; and
a lead-free solder alloy connecting said electrode to said conductor pattern, said lead-free solder alloy containing: Bi with a concentration not exceeding 60.0 wt %; In with a concentration not exceeding 50.0 wt %; one or more elements selected from a group consisting of Ag, Zn, Ge, Ga, Sb and P, with a concentration equal to or larger than 1.0 wt % but lower than 5.0 wt %; and Sn as a remaining component of said lead-free solder alloy.
Another object of the present invention is to provide an electronic apparatus, comprising:
a substrate;
a conductor pattern provided on said substrate;
an electronic component mounted upon said substrate in electrical connection with said conductor pattern, said electronic component having an electrode projecting therefrom; and
a lead-free solder alloy connecting said electrode to said conductor pattern, said lead-free solder alloy containing Sn, Ag and Bi, with respective concentrations set such that said lead-free solder alloy has a melting temperature lower than a predetermined heat-resistant temperature of said electronic component.
Another object of the present invention is to provide a soldering rig for soldering a work, comprising:
soldering unit for soldering a work by causing a reflow of a lead-free solder; and
a cooling unit for cooling said work at a part where a soldering has been made, to solidify said lead-free solder.
According to the present invention as set forth above, one can obtain a solder alloy free from Pb while maintaining excellent mechanical strength in the solidified solder alloy. Thereby, the problem of hazard to biological bodies as well as the problem of environmental pollution are successfully eliminated. Further, by optimizing the composition of the solder alloy, it is possible to reduce the melting temperature of the solder alloy lower than a melting temperature of a conventional solder alloy that contains Pb, while maintaining sufficient mechanical strength. Thereby, the damage applied to the work or electronic component as a result of soldering is reduced. Associated with the reduced temperature of soldering, the preparation of the work for soldering is substantially simplified, and the cost of the work is also reduced by using less expensive materials. By cooling the solder alloy rapidly, it is possible to maximize the elongation of the solidified solder alloy.
Other objects and further features of the present invention will become apparent from the following detailed description when read in conjunction with the attached drawings.